Traditionally, vehicle drive shafts have been formed of a steel tube having a high flexural modulus with a forged yoke welded to each end of the steel tube. With both the tube and the yokes formed of steel the drive shaft is a relatively heavy structure.
At certain rotational speeds, a drive shaft can become dynamically unstable. The critical speed at which the instability occurs is generally proportional to the flexural modulus of the shaft and its moment of inertia and generally inversely proportional to the weight of the shaft and its length. To maintain an acceptably high critical speed with a tubular steel drive shaft, the drive shaft in many instances is formed of short multiple sections and shaft support bearings are utilized along the length of the drive shaft which act to rotationally support the shaft sections.
Recently there has been considerable activity in the development of composite drive shafts which are composed of a fiber reinforced resin tube or shaft and light weight metal, such as aluminum, yokes. The composite drive shaft achieves a substantial weight reduction as compared to a steel drive shaft and due to the lighter weight, a one piece composite shaft can replace the multi-section steel shafts, with the resultant elimination of the shaft support bearings which are utilized with a multi-section steel shaft.
However, a problem in the production of a composite drive shaft has been the lack of an adequate connection between the fiber reinforced resin tubular member and the yokes. In one approach to providing an adequate connection between the tube or shaft and the yokes, the ends of the tube, which surround the sleeve portion of the yoke, are connected to the sleeve portion by rivets. In another approach, as shown in U.S. Pat. No. 4,279,275, the sleeve portion of the yoke is provided with a plurality of longitudinally extending grooves and the resin impregnated fibrous material, when producing the tubular member, is wound circumferentially over the grooves to provide an improved mechanical connection between the tube and the yokes.
In the U.S. Pat. No. 4,358,284 the sleeve portion of the yoke is provided with circumferential extending grooves or threads and the fibrous material is wound in the grooves to provide an improved attachment, while in U.S. Pat. No. 4,380,443 a plurality of angularly extending pins are employed to interconnect the wound tube with the sleeve portion of the yoke.
U.S. Pat. No. 4,248,062 proposes to increase the bond between the wound tube and the sleeve portion of the yoke by employing a specific winding pattern including longitudinal helical and circumferential windings.